Background There is a growing awareness of the need for discussion of advance directives (ADs) in the ambulatory setting, but rates of completion remain low. Clarification of patients' perceptions and knowledge would help in designing future strategies. Methods This is a prospective study of adult ambulatory patients at four academic internal medicine clinical sites at the University at Buffalo during a 6-week period in 2004. We obtained data using a standard instrument administered by a research assistant. The data included demographic variables, patients' awareness of and familiarity with specific ADs, and whether the patient had any ADs. Patients also were asked about attitudes concerning the appropriateness of ADs. We performed multivariate logistic regression on the variables. Results Of 508 patients, 86.2% were unfamiliar with the term "advance directives," but 93.5% were familiar with one or more specific kinds of ADs. Some 43.1% of patients claimed to have completed an AD, but of those who said they had, only 25% thought their provider had a copy. Multivariate logistic regression demonstrated significant correlation between having completed an AD and age, reading ability, and educational level (all P < .001). Conclusions A large number of patients in an ambulatory internal medicine practice knew about ADs and believed they had completed such documents, but these documents were often not in the chart. Many patients believe discussions of ADs are not appropriate for them. A better understanding of this phenomenon will help in promoting effective advance care planning.

A series of myoglobin active site analogues (1-6) has been synthesized and characterized. These synthetic models differ in their cavity dimensions, and have been designed to demonstrate the effects of steric factors on O-2 and CO binding affinities. Quantitative gas titrations were employed to measure these affinities, yielding M values that are strikingly lower than those reported for hemoglobin and myoglobin. The 1,4,7-triazacyclononane-capped porphyrin 1 has about 1200 times the CO affinity but only about 10 times the O-2 affinity of the cyclam-capped porphyrin 2, suggesting a more open gas binding cavity for 1. The cavity dimensions and conformation of 2 were determined by single-crystal X-ray structural analysis of the Zn analogue 7. This paper unequivocally demonstrates that steric effects can control the ratio of O-2/CO binding constants.